Warren Bennis
Know thyself was the inscription over the Oracle at Delphi. And it is still the most difficult task any of us faces. But until you truly know yourself, strengths and weaknesses, know what you want to do and why you want to do it, you can not succeed in any but the most superficial sense of the word. The leader never lies to himself, especially about himself, knows his flaws as well as his assets, and deals with them directly. You are your own raw material. When you know what you consist of and why you want to make of it, then you can invent yourself.
Leaders are people who are able to express themselves fully, they know who they are, what their strengths and weaknesses are, and how to fully deploy their strengths and compensate for their weaknesses. They also know what they want, why they want it, and how to communicate what they want to others, in order to gain compensation and support. Finally, they know how to achieve their goals. The key to full self-expression is understanding one's self and the world, and the key to understanding is learning -- from one's own life and experience.